Plug contactor



April 1961 w. R. SCHELLER 2,980,883

PLUG CONTACTOR Filed Feb. 17. 1959 INVENTOR. (JILFRED R.$CHELLE R UnitedStates PLUG CONTACTOR Filed Feb. 17, 1959, Ser. No. 796,750

2 Claims. (Cl. 339-252) Wilfred This invention relates to plugcontaotors for use with the plugboard or circuit connecting panel of anelectrical calculating or accounting machine or the like, and moreparticularly to an improvement in the construction of the spring detentsystem of the plug contactor.

A variety of forms of spring systems for plug contactors have heretoforebeen proposed, some involving separate spring elements assembled in aplug shell and others including spring elements of a form difficult tomanufacture and maintain to the uniform shape and close tolerancesdesired for uniform detention characteristics.

Among the objects of the present invention is the provision of a plugcontactor which is simpler and more economical in construction thanprevious plugs of this type, avoiding the use of added spring partswhich are relatively costly in assembly and material. It is also anobject to provide such a plug with a spring system which is rugged andwill retain substantially its original characteristics over a long life.A further object is the provision of a spring system for such a plugwhich is integral with the plug shell and of a character easilysusceptible to precise control of shape.

Other objects and attainments of the present invention will becomeapparent to those skilled in the art upon a reading of the followingdetailed description when taken in conjunction with the drawings inwhich there is shown and described an illustrative embodiment of theinvention; it is to be understood, however, that this embodiment is notintended to be exhaustive nor limiting of the invention but is given forpurposes of illustration in the invention and the principles thereof andthe manner of applying it in practical use so that they may modify it invarious forms, each as may be best suited to the conditions of aparticular use.

In the drawings:

Figure 1 is a perspective view of an embodiment of a plug contactorincorporating features of the present invention;

' Figure '2 is a sectional view in elevation of the plug contactor ofFigure 1 in fully inserted position in a plugboard;

Figure 3 is a fragmentary plan view of the plug contactor of Figure 1;

Figure 4 is a sectional view taken at lines 4-4 of Figure 3; and

Figure 5 is a sectional view taken at lines 55 of Figure 3.

The particular type of plug co'ntactor to which this invention relatesis especially adapted for use in the plugboard wiring system of anelectrical accountingor calculating machine, or the like, which systemtypically includes a fixed plugboard carrying a set of permanentcontacts arranged in rows and columns. A movable plugboard removablycarrying a corresponding set of plug contactors is arranged to bring thesets of contact elements into engagement so as to complete theelectrical circuits desired.

' atent Referring now to Figures 1 to 5, a plurality of apertures 2 ofplugboard 4 receives a plurality of plug contactors, such as the pluggenerally designated at 6, in an array for interengaging at theirprojecting nose 8 the set of contacts on a fixed plugboard, not shown.

Plug 6 comprises a hollow cylindrical sleeve or shell 10 of a resilientconductive metal, such as nickel-plated full hard brass, preferablyrolled up from flat sheet stock into tubular form with a butt seam 12extending longitudinally of the sleeve along its bottom center line,Figures 4 and 5. At its rearward end, the left-hand end as viewed inFigure 2, shell 10 is provided with integral means 14 by which conductor16 is mechanically and electrically attached to the plug. Preferablyattaching means 14 is formed into a ferrule from an initially U- shapedcross-sectional configuration, the ferrule being tightly crimped aroundthe wire core of conductor 16 by cold forging techniques conventional inthe art as illustrated, for example, in Patent No. 2,600,012, issuedJune 10, 1952, to James C. Macy.

An insulating sheath 18 of a suitable resin such as polyvinyl chloridepreferably is molded around the rear end of the plug and adjacentportions of the insulation of conductor 16. Sheath 18 insulates theferrule or attaching means 14 and supports the adjacent portionofconductor 16 to increase its resistance to bending fatigue whileconveniently serving as a handle for manipulating the plug.

At the rearward end of the cylindrical body of shell 10 adjacent theforward end of sheath 18 an integral circumferential bead 20 isprovided, which bead is arranged to engage the face of plugboard 4adjacent edge portions of an aperture 2 to act as. a stop for limitingmovement of the plug into the plugboard.

To form the spring detent system for the plug a pair of parallel, closedand longitudinally extending slots 22 and 24 define and releasetherebetween a spring beam 26 anchored at both ends to the body of shell10, preferably at points in diametric opposition to seam 12. Adome-shaped boss 28 positioned intermediate the length of spring beam 26serves as a detent which will be depressed with beam 26 as sleeve 10 ispushed into aperture "2, ultimately to snap resiliently behind one edgeof the aperture as bead 20 engages the plugboard face at the other endof the aperture. The degree of slope of the sides of boss 28 in partcontrols the force required to insert and withdraw the plug. Theretentive force of the detent may further be varied according to theconditions of a particular use through alteration of the springcharacteristics of beam 26, for example, by variation in the length anddistance apart of slots 22 and 24, or the cross-sectional configurationof beam 26 as desired. Typically, the slots may be spaced approximatelyrelative to the shell circumference and widened to the degree necessaryto yield a spring beam of the desired rigidity. In cross-section beam 26preferably follows the curvature of shell 10, boss 28 being disposed inthe forward half of beam 26 advantageously locating at least half thelength of the slots within the plugboard thickness on insertion of theplug.

Forwardly of the spring detent, the nose 8 of the plug converges topresent a rounded tip formed from three triangular sections, best shownin Figure 5, in a manner conventional in the art.

For tolerance reasons the circumference of shell 10 may not always besufficiently closely matched to the diameter of aperture 2, nor thedistance between bead 20 and boss 28 to the plugboard thickness, toavoid an undesired loose fit of the plug on insertion. To assure a snugfit a short section 30 of the rear portion of beam 26 is flattened todefine a plane approximately tangent to shell 10 thereby increasing itseffective circumference Patented Apr. 18, 1961 to at least the largestaperture diameter contemplated in use. That is, the edges of flatsection 30 will extend beyond the circumference of the shell. Forsmaller diameter apertures flat section 39 will result in beam 26 beingslightly depressed to provide a resilient takeup means for the diameterdifierential between the plug and aperture. Alternatively, or inaddition, a slight convexity may be imparted to beam 26 over its length,as best shown in Figure 4, in assurance of a resilient lateral bias ofthe plug against the aperture sidewalls.

It will be apparent to those skilled in the art that plug 6, apart fromany insulation sheath 18, may be wholly and simply formed from a singlesheet metal blank by conventional die stamping and forming techniques,yet achieving a rugged and economical construction which is reliable andfoolproof in use. I

I claim:

1. In a plug contactor for insertion in an aperture in a plugboard, -ahollow cylindrical sheet metal sleeve, a pair of longitudinallyextending slots circumferentially biasing the plug contactor laterallyagainst the aperture sidewalls on insertion.

2. A plug contactor according to claim 1 wherein said beam is convexsubstantially over its full length along the sleeve. 9

References Cited in the file of this patent UNITED STATES PATENTS2,691,145 Watts Oct. 5, 1954 FOREIGN PATENTS 403,864 Great Britain Ian.4, 1934 567,798 Great Britain Mar/5, 1945

